Question for amp techs and moders familiar with the 6505+

[TSE]

Looking at the schematic for the regular 6505 c19 looks like a treble bleed circuit, I can't find the schematic for the plus version and want to confirm c19 does the same function. I want to take it out if it is a treble bleed cap and it's the same for the 6505+. Any and all help is greatly appreciated.

 

[zzmoore]

Re: Question for amp techs and moders familiar with the 6505+

If I am looking at the same schem you are.....
I do not understand what that first RC filter (is it 10k/39pf.?) is for. Guess it is part of the Peavey high gain game plan.
Anyway.....I would say that next one is a High Pass Filter.? The 100nf sets up a filter with the 1M grid leak resistor. The smaller the cap value, the higher the frequencies it will pass.
You could just jumper it and see what you hear. I would be tempted to take all that out and see what it sounds like. Just leaving the 1M and the 68k.
Experiment and see what works best for you.
That is my stab at it.

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Yea, the goal is to lower the treble when the gain is low like 10 o clock to noon. It looks to me like c19 acts as a treble bleed cap so when you turn the gain down it retains treble frequencies. Just like on a guitar. I want to discard this feature because I never use the gain above 4 and would like the treble to be less piercing. I don't mind brightness, it just sounds harsh to me and when I turn it down it gets muddy.

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Please use reference designators, I'm no pro lol

 

[Maynardo]

Re: Question for amp techs and moders familiar with the 6505+

post the schematic your looking at

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

http://www.mrbobo.com/mods/5150evh.pdf

 

[Maynardo]

Re: Question for amp techs and moders familiar with the 6505+

Wow that looks pretty crappy!... anyways 2 things: have you opened the amp?... a lot of times bright caps are soldered directly to the gain pot, so even if you don't have the schematic for the 5150II (aka 6505+) you could take it out fairly easy, if you wanna keep modding, you can look that tonestack... it has two treble caps in parallel a 470p and a 100p, if you take out the 100p out the high mids will shift a little to the lower end of things making the amp less harsh at any gain level, you could clip just one of the legs of the cap and check if that is a good change for your ears. That way is very easy to go back

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Awesome, thanks a lot

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

You're talking about c60 and c14?

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

What would happen if I removed c19 as well? Would it do what I had originally hypothesized?

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

http://music-electronics-forum.com/attachments/7812d1264619110-6505-schemvc0.jpg

That link is a jpeg of the 5150II. It looks like they removed C60 (the 470p cap I *think* you mentioned. C19 (.001uf) is still there and I'll try removing that and see what happens. Amp modification rocks!

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Bump

 

[Maynardo]

Re: Question for amp techs and moders familiar with the 6505+

This one has two tone stacks, in the crunch channel they got the two treble caps I mentioned before... in the lead channel nop

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

I'm not really worried about the crunch channel. I mainly use the lead and the crunch I use to boost solos when I need a volume boost. Usually have the lead post at 3 or 4 and the crunch post at 4 or 5 with the bright function disengaged.

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Ok I see c150 being the 100pf and c152 is 470pf. The crunch channel is fine, the lead is my primary concern.

 

[Maynardo]

Re: Question for amp techs and moders familiar with the 6505+

So why don't you just open the amp y clip one the legs of the c19 to see if that does it for you, otherwise I'm not quite sure the schematic is correct, the third stage is missing the fizz filtering cap in the plate resistor, I mean that stage is copied off the SLO 100 and it's got that super cold bias, I'd check if that part is accurate, if it is putting there a 0.001uF cap across the plate resistor would definetly remove some harsh high end.

Read more about it if you're interested here: http://www.ampbooks.com/home/classic-circuits/soldano-slo-preamp-3/

 

[zzmoore]

Re: Question for amp techs and moders familiar with the 6505+

http://www.prowessamplifiers.com/sc...y_6505_Plus_112_Combo_Schematics_and_BOM.html

Guess I was looking at the wrong schem. Could not follow you guys that well. The one I was peeking at is above.
I was thinking to jump C19.
Then maybe remove R9 C22. Can always restore it.
I thought he was looking for the 6505. Sorry for the bad advice.
best

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

No worries, is there any difference electrically between jumping c19 as opposed to clipping it out of the circuit? And if c19 is taken out would the 1 Meg resistor that's in parallel with c19 have to go as well?

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Looking at the 5150ii schematic^

 

[TSE]

Re: Question for amp techs and moders familiar with the 6505+

Ok so I just clipped c19 and it seemed to do the trick. I'm not going to worry about the 1 Meg resistor in parallel. It's much quieter as well. Idk why they even put that cap there in the first place. Peavey amps are notorious for their excessive treble and the 6505+ is no exception. Definitely less fizz and peeky high end when using gain at 3-5. I can't blast it yet because I live in an apartment, but this Sunday I'll be able to turn it to high volume practice levels. So far it sounds much better. If I need lots of treble it's still there via presence knob.